The Study On Emulsifying Properties Of Sweet Potato Hydrolysates With High Pressure Treatment

Five kinds of proteases were selected to process sweet potato protein under four pressures respectively to study its effect on emulsifying properties of sweet potato protein. After that, sweet potato protein was enzymed after a pretreatment of high pressure to study its effect on emulsifying properties of sweet potato protein. Sweet potato hydrolysates were prepared under the condition that the emulsifying activity was the best.The effect of different environmental factors on emulsifying properties of hydrolysates were studied by measuring microstructure, particle size, emulsifying activity, emulsifying stability, rheological property of its emulsion and its hydrophobicity. Results were as follows:(1) The emulsifying activity of sweet potato hydrolysates obtained with Papain under 300 MPa was found the best. Under this condition, the further study for time was processed, it was found that the optimum treatment time was 6 minites.(2)After the treatment of 10 minites under 400 MPa and 600 MPa, sweet potato protein was enzymed with five kinds of enzymes.It was found emulsifying properties of sweet potato protein will be reduced by enzymolysis after high pressure.(3)With the increase of NaCl concentration, the emulsifying activity of sweet potato hydrolysates was decreased that was only 32.32m2/g when NaCl concentration was 1.0M. Accordingly, with the increase of NaCl concentration the particle size was also increased. Hydrophobicity was maximum at NaCl concentration of 0.2M, was minimum at 0.6M. The emulsifying stability was maximum at 0.4M and there were no significant differences at other concentrations. With the increase of p H value, the emulsifying activity increased significantly. At p H3, the emulsifying stability was maximum, then it increased with the increase of pH, but the value is less than that at pH3. With the increase of p H, the particle size was significantly reduced while hydrophobicity increased.(4)The increase of product concentration reduced EAI and ESI of emulsion, maximum value was obtained at a concentration of 0.1%(w/v). At a shear rate of 1s-1, the apparent viscosity was also the highest at a concentration of 0.1%(w/v), and with the increase of shear rate shear-thinning phenomenon was appeared. With the increase of the oil phase volume fraction, EAI gradually increased. ESI was the highest up to 30.41 minites at 5%, then with the increase of the oil phase volume fraction, ESI also increased, but lower than that at 5%. Accordingly, when the shear rate was 1s-1, the apparent viscosity was the maximum at the oil phase volume fraction of 45%.Therefore, proper enzymolysis under high pressure can significantly improve the emulsifying activity of sweet potato protein, and the environmental factors have a significant impact on the emulsifying properties of hydrolyzates. The theoretical support for the application of sweet potato protein as emulsifier in food industry was provided by this paper.